1. Field of the Invention
The invention relates to means to support a cooler tube of a planetary cooler in planetary fashion about a rotary kiln.
2. Description of the Prior Art
Rotary kilns, such as are used for example in the cement industry for the burning of cement clinker have, normally at the clinker outlet end, a cooler for cooling the clinker before further treatment. A well known cooler type is the planetary cooler, consisting of a number of cooler tubes mounted in a ring around the outlet end of the kiln and extending substantially parallel to the longitudinal axis of the kiln. In such an arrangement, the tubes have the same general inclination as the kiln.
At the inlet end of a cooler tube, the kiln and the tube are usually in fixed connection with one another; however, the tube, at its outlet end, is usually supported by a bracket or similar means attached to the outer kiln shell to provide a bearing with a limited axial movement in relation to the tube. This movement is necessary because of the cooler tubes, which are more rigid and which operate at a lower temperature than the kiln, move slightly in the axial direction in relation to the kiln during operation due to sagging which occurs in the kiln which produces a slight axial shortening of the kiln. This sagging is most noticeable at the hot end of the kiln which corresponds to the outlet end of the cooler tube. In the bearing of such a cooler tube support, there is a great amount of friction during operation of the kiln since the bearing bracket attached to the outer kiln shell follows the movement of the kiln, whereas the cooler tube remains rigid.
Efforts have been made to avoid or reduce the disadvantageous effects of these frictional forces upon the cooler tube by supporting the tube by special sliding surfaces or rollers provided between the tube and the bearing. Such an arrangement requires feeding of a lubricant to the sliding surfaces. As yet, no acceptable means for lubricating these surfaces has been developed.
A member connecting two adjacent cooler tubes and the kiln is likewise known. In this arrangement, the support member is rigidly connected to the cooler tubes by bolts and hinged on the kiln shell, but due to the sagging of the kiln, the rigid connection at the cooler tubes is subjected to destructive forces during operation.
Annular rims affixed to the periphery of the rotary kiln casing in order to support all the satellite cooling tubes are also known in the art. For example, West German Pat. No. 24,24,224.8 to Polysius AG relates to a rotary kiln for the heat-treatment of material and having a number of satellite cooling tubes distributed uniformly round the rotary kiln periphery at the exit end of the kiln, the inlet ends of these tubes being connected by short inlet pipes to the interior of the rotary kiln, and each tube being supported on the rotary kiln casing by two support bearings, whereof the rearmost support bearing, as seen in the material feed direction, holds the corresponding cooling tube so that this tube can move axially.
I have invented a new means to support a cooler tube in planetary fashion about a rotary kiln. The new movable support allows for independent cooler and kiln sagging due to heat expansion and gravity, in such a way that the difficulties so far encountered in connection with reducing the friction and bending forces arising between a cooler tube and its support are overcome. It also facilitates the hitherto rather complex mounting of cooler tubes on the kiln proper, which is becoming increasingly more difficult with the increased size of kilns and cooler tubes.